ARP configuration

Overview

Introduction to ARP

The Address Resolution Protocol (ARP) is used to resolve an IP address into an Ethernet MAC address (or physical address).

In an Ethernet LAN, a device uses ARP to resolve the IP address of the next hop to the corresponding

MAC address.

For more information about ARP, see H3C WX Series Access Controllers Layer 3 Configuration Guide.

Introduction to gratuitous ARP

Gratuitous ARP packets

In a gratuitous ARP packet, the sender IP address and the target IP address are the IP address of the sending device, the sender MAC address is the MAC address of the sending device, and the target MAC address is the broadcast address ff:ff:ff:ff:ff:ff.

A device sends a gratuitous ARP packet for either of the following purposes:

• Determine whether its IP address is already used by another device. If the IP address is already used, the device will be informed of the conflict by an ARP reply.

•

Inform other devices of the change of its MAC address.

Learning of gratuitous ARP packets

With this feature enabled, a device, upon receiving a gratuitous ARP packet, adds an ARP entry that contains the sender IP and MAC addresses in the packet to its ARP table. If the corresponding ARP entry exists, the device updates the ARP entry.

With this feature disabled, the device uses the received gratuitous ARP packets to update existing ARP entries, but not to create new ARP entries.

Displaying ARP entries

Select Network > ARP Management from the navigation tree to enter the default ARP Table page shown

in Figure 120

. All ARP entries are displayed on the page.

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Figure 120 ARP Table configuration page

Creating a static ARP entry

1.

2.

Select Network > ARP Management from the navigation tree to enter the default ARP Table page

shown in Figure 120

.

Click Add to enter the New Static ARP Entry page, as shown in

Figure 121 .

Figure 121 Adding a static ARP entry

3.

4.

Configure the static ARP entry as described in Table 59 .

Click Apply.

Table 59 Configuration items

Item Description

IP Address Enter an IP address for the static ARP entry.

MAC Address Enter a MAC address for the static ARP entry.

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Item Description

Enter a VLAN ID and specify a port for the static ARP entry.

VLAN ID

Advanced

Options

Port

IMPORTANT:

The VLAN ID must be the ID of the VLAN that has already been created, and the port must belong to the VLAN. The corresponding VLAN interface must have been created.

Removing ARP entries

1.

2.

Select Network > ARP Management from the navigation tree to enter the default ARP Table page

shown in Figure 120

.

Remove ARP entries:

To remove specific ARP entries, select target ARP entries, and click Del Selected.

To remove all static and dynamic ARP entries, click Delete Static and Dynamic.

To remove all static ARP entries, click Delete Static.

To remove all dynamic ARP entries, click Delete Dynamic.

Configuring gratuitous ARP

1.

2.

Select Network > ARP Management from the navigation tree.

Click the Gratuitous ARP tab to enter the page shown in Figure 122

.

Figure 122 Gratuitous ARP configuration page

3.

Configure gratuitous ARP as described in Table 60

.

Table 60 Configuration items

Item Description

Disable gratuitous ARP packets learning function

Disable learning of ARP entries according to gratuitous ARP packets.

Enabled by default.

Send gratuitous ARP packets when receiving ARP requests from another network segment

Enable the device to send gratuitous ARP packets upon receiving ARP requests from another network segment.

Disabled by default.

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Static ARP configuration example

Network requirements

To enhance communication security between the AC and the router, configure a static ARP entry on the

AC.

Figure 123 Network diagram

Configuration procedure

1.

Create VLAN 100: a. b.

Select Network > VLAN from the navigation tree to enter the default VLAN page.

Click Add. c. d.

Enter 100 for VLAN ID, as shown in Figure 124

.

Click Apply.

Figure 124 Creating VLAN 100

2. a. b. c.

Add GigabitEthernet 1/0/1 to VLAN 100:

On the VLAN page, click the icon of VLAN 100.

Select the Untagged Member option for GigabitEthernet1/0/1.

Click Apply.

144

Figure 125 Adding GigabitEthernet 1/0/1 to VLAN 100

3.

Configure VLAN-interface 100: a.

Select Device > Interface from the navigation tree. b. c. d.

Click Add.

On the page that appears, select Vlan-interface from the Interface Name list, and enter 100, select the Static Address option for IP Config, enter 192.168.1.2 for IP Address., and select 24

(255.255.255.0) for Mask.

Click Apply.

145

Figure 126 Configuring VLAN-interface 100

4.

Create a static ARP entry: a.

Select Network > ARP Management from the navigation tree to enter the default ARP Table page. b. c. d.

Click Add.

On the page that appears, enter 192.168.1.1 for IP Address, enter 00e0-fc01-0000 for MAC

Address, select the Advanced Options option, enter 100 for VLAN ID, and select

GigabitEthernet1/0/1 from the Port list.

Click Apply.

146

Figure 127 Creating a static ARP entry

147